Appendix A Need More PCIe Slots?
Multiple PCIe Expansion System Configurations
The PCI Express Local Bus Specification defines the bus as hierarchical, where logical PCI to PCI Bridges (PPBs) may be used to add "levels" to the PCI bus hierarchy within a PCIe switch. Because hierarchies are organized systems arranged into different levels, you can take advantage of this automatic organizing and layering to expand the number of available PCIe slots beyond the number available in your computer’s motherboard.
You can easily add two or more Magma expansion systems to your current system in either a
1.In a desktop computer, the BIOS enumerates automatically behind logical PCI bridges. In the Magma configuration, the BIOS looks beyond the Host card to find any PCIe cards installed in the expansion chassis behind a PCIe switch. The PCIe switch, in turn, emulates logical PRBs. The BIOS can then configure the cards and allocate resources. Empty PCIe slots are ignored during configuration.
In theory, your computer “should” be able to travel across up to 255 PCIe buses to identify and configure all installed PCIe cards. The 255 PCI bus limit is actually a theoretical maximum. The practical limit is somewhat lower and differs from one system to another, but should still be a fairly large number.
In a desktop computer the bus numbers tend to be lower (0, 1, 2, etc.). Once the BIOS is finished configuring everything and assigning resources, the Operating System starts loading and activates the PCIe cards found.
When adding more Expansion Systems to an existing system, be sure to connect and test them
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